Four car bombs exploded at dusk Wednesday, killing at least 23 people, including sidewalk diners and passengers at a bus station. The coordinated attacks served as a chilling reminder of how potent militants remain in the capital despite around-the-clock American and Iraqi troop patrols.

In all, at least 32 people were killed across Iraq, including a prominent Sunni law professor assassinated by gunmen. Jassim al-Issawi (search) was a former judge who put his name forward at one point to join the committee drafting Iraq's constitution. The assassination appeared aimed at intimidating Sunni Arabs willing to join Iraq's efforts to create a stable political system.

The U.S. military said three U.S. soldiers were killed a day earlier during combat operations west of Baghdad near the insurgent stronghold of Ramadi (search). At least 1,727 members of the U.S. military have died since the war began in 2003, according to an Associated Press count.

The first three car bombs — clearly coordinated — went off almost simultaneously only blocks apart in the predominantly Shiite neighborhood of Shula where al-Issawi was killed only hours earlier.

Two bombs exploded in front of a pair of restaurants, killing at least 11 and wounding 28. "The body parts of the dead were scattered everywhere, along with fragments of broken glass from nearby shops and the meat from the meals," said police Maj. Musa Abdul Karim, who was at the scene. "Blood was everywhere."

The third car bomb exploded when a homicide bomber rammed a nearby bus station, killing at least 8 and wounding 20, police said.

About 15 minutes later, a suicide car bomber struck an Iraqi army patrol in a nearby suburb, killing at least four bystanders, police said. The dead included a woman and a child. No Iraqi soldiers were among the wounded.

A fifth car bomb targeting a U.S. military convoy missed, killing instead three Iraqis and wounded seven in the northern city of Mosul (search), officials said.

Four Iraqis also were killed in two roadside bombs and a group of children drove their bicycles over a bomb planted beneath the ground in Baqouba, northeast of the capital. A 9-year-old boy was killed and two others, aged 6 and 7, were wounded.

Al-Issawi's killing, potentially the most politically significant act of violence since Prime Minister Ibrahim al-Jaafari (search) came to office nearly two months ago, marked the first direct attempt to scare moderates away from political participation.

It sent a powerful message to the Sunni Arab community to either boycott involvement in the fledgling government or risk death.

Insurgents bent on starting a civil war to overthrow Iraq's U.S.-backed government have maintained nearly eight weeks of relentless attacks, killing at least 1,230 people since April 28, when al-Jaafari announced his Shiite-dominated government.

Al-Issawi, thought to be 50, was shot dead with his son, according to Abdul-Sattar Jawad, editor-in-chief of al-Siyadah, a daily newspaper where the lawyer was a contributing editor.

In Brussels, Belgium, an international conference adopted a declaration of support for the struggling nation, backing the Iraqi government's "efforts to achieve a democratic, pluralist, federal and unified Iraq."

At the meeting, U.S. Secretary of State Condoleezza Rice vowed the Iraqi insurgency would be defeated.

"Terrorism can be defeated in Iraq," Rice said. "And when it's defeated in Iraq, at the heart of the Middle East, it will be a death knell for terrorism as we know it."

But al-Issawi's killing and the Shula bombings provided fresh evidence of the insurgents' ability to strike with impunity in the heavily protected Iraqi capital, where U.S. and Iraqi forces hunt insurgents patrol around the clock.

Deputy Prime Minister Ahmad Chalabi, a senior Shiite politician and a former Washington insider, condemned the assassination and renewed his government's commitment to include Sunni Arabs in drafting the constitution.

"The constitution will be the document that represents the unity of Iraq," he vowed in remarks to reporters after meeting leaders of the Association of Muslim Scholars, an influential and militant Sunni Arab group known to have links to the insurgency.

Leaders of the Sunni Arab minority also condemned al-Issawi's assassination, linking it to what they said was a plan to eliminate key minority figures ahead of the crucial task of writing the basic law. There was no immediate claim of responsibility for al-Issawi's assassination, but Abu-Musab al-Zarqawi al-Qaida in Iraq has threatened to kill Sunni Arabs cooperating with the government or the United States.

"The assassination of professor Jassim al-Issawi comes within an organized campaign aiming to liquidate all Sunni figures who will play an important role in the upcoming political process," said Salih al-Mutlak, whose Sunni Arab group has been negotiating the minority's participation in the constitutional process.

Al-Issawi was on a list of Sunni Arab candidates included in an earlier round of negotiations to join parliament's 55-member constitutional committee. He later withdrew his candidacy and a new list of 15 members and 10 advisers was submitted to parliament earlier this week.

The 15 are to join the 55 legislators on a parallel body that would make decisions by consensus and refer them to the original 55 for endorsement.

Sunni Arabs, who dominated Iraq for decades, lost power when Saddam, their last patron and a Sunni, was ousted. Their boycott of historic elections in January further sidelined them. They won just 17 of parliament's 275 seats, leaving the Shiites and Kurds, the two communities they had oppressed, with the remainder.

But Sunni Arab participation in the political process — for which the United States and the European Union have repeatedly called — is essential for Iraq's passage to democracy.

Parliament has until Aug. 15 to draft the new constitution, which will be put to a referendum two months later. If ratified, it will be the basis for a general election in December, giving Iraq its first, full-term elected government in decades.